You need to treat the CU and the analog hookup panel (driver stations) as separate units, and only connect one or the other to the track, not both at the same time.
The main reasons is that the CU connect both lanes into one single lane by using jumper cables between lane-1 and lane-2 in the CU track piece. To use the track for analog you must take the back cover off the CU track piece and move the track power cables from the rails and connect them to a 4PDT switch. Then wire track power cables from the switch to the rails (see below).
Here is a simple sketch I mocked up:
Another issue that cause problems is that on Carrera digital, the left rail is positive and the right rail is negative, this is opposite from the Carrera analog connection track piece, and other common analog wiring methods. This results in two issues:
1. in analog mode, the cars will travel in the opposite direction
2. Any digital accessories and LC's that is connected directly to the track will get power with opposite polarity than what they are designed for, when the track is in analog mode. This might destroy the accessories and LC's over time. This has not been proven, but it's a theory I have.
A simple solution is to cross the wires on the output side of the analog hookup panel (driver stations), this will ensure the track gets the same polarity as when in digital mode, but the direction of travel in analog mode will depend on the polarity of the controller/panel.
A better solution is to power all LC's and digital accessories directly from the CU output (make a power hub between the CU and the 4PDT switch in my sketch above). Then you can use a directional switch after the analog hookup panels and run the track analog in both directions without the risk of destroying the digital pieces.
As for power taps to distribute power evenly around the track, start the first tap on first normal track piece after the CU and make sure the lanes are isolated and the polarity is the same. Always connect the same rail to the same rail on the next tap.
Note: My sketch does not show how the analog driver stations should be wired, there are several guides on how to do this here on SCI and on the SCC website.